1. Field of the Invention
This invention relates to additives to improve the flow and filterability properties of distillate fuels at low temperatures, to fuels containing the additives and especially to concentrates of the additives for incorporation into the fuel. Particularly, the invention relates to an additive concentrate comprising an oil solvent, an ethylene-ester copolymer, a nitrogen-containing amide and/or salt of an aliphatic dicarboxylic acid or anhydride, and an oil soluble compatibility improving additive which lowers the pour point of said concentrate and which improves the compatibility of said copolymer and said nitrogen compound.
2. Description of the Prior Art
Additive systems and concentrates comprising nitrogen containing amide or amine salts as used in the present invention are disclosed in U.S. Pat. No. 4,211,534 which discloses an additive flow improver of an ethylene polymer or copolymer, a second polymer of an oil soluble ester and/or C.sub.3 and higher olefin polymer and a nitrogen containing compound.
European patent application No. 82301556.5 having Publication No. 0061894 discloses the use of nitrogen containing compounds in combination with certain ethylene/vinyl acetate copolymers as distillate additives which may be supplied in the form of concentrates.
U.S. Pat. No. 3,982,909 discloses an additive system comprising amides, diamides and ammonium salts alone, or in combination with certain hydrocarbons such as microcrystalline waxes or petrolatums, and/or an ethylene backbone polymeric pour depressant, the combination being useful as a flow improver for middle distillate fuels.
U.S. Pat. No. 3,850,587 shows use of certain acids, especially aromatic acids, to improve the compatibility of the amine salt/amides of alkenyl succinic acid and ethylene-vinyl acetate copolymers in oil concentrates used for incorporation into distillate fuels.